If you have a smartphone that you are happy with now then I would hold off until the update because, as most have said, it's been out for quite some time.
If you don't have a phone that is satisfying you then I would just go ahead and buy the iPhone 5. Thats at least 6 months if the 5s is released in June which I don't think it will be. With my expectation of october, thats all summer of taking pictures, being out and about with the beautiful weather and its awesome to have a phone then. In my opinion the "S" updates are pointless to wait for unless it's within 2 months away
Just my 2 cents tho